Stockholders' Equity (Details) (USD $) In Thousands, except Share data, unless otherwise specified	1 Months Ended	3 Months Ended	9 Months Ended	12 Months Ended
	Jun. 30, 2012	Sep. 30, 2013	Sep. 30, 2013	Dec. 31, 2012
Stockholders' equity
Weighted-average grant date fair value of awards (in dollars per share)		$ 54.59
Maximum stock repurchase amount approved by Board of Directors	$ 200,000
Remaining stock repurchase amount approved by Board of Directors			79,300
Number of shares repurchased		0	0	2,765,000
Repurchase of common stock, payments				120,700
Average stock price of shares repurchased (in dollars per share)				$ 43.66
2006 Equity Incentive Plan (2006 Plan)
Stockholders' equity
Common stock reserved for issuance (in shares)		6,000,000	6,000,000
Maximum number of shares that may be issued through the exercise of incentive stock options		4,500,000	4,500,000
2006 Equity Incentive Plan (2006 Plan) | Nonvested stock units issued (NSUs)
Stockholders' equity
Number of shares granted		298,250	15,750
Weighted-average grant date fair value of awards (in dollars per share)			$ 57.29
Future unrecognized compensation cost, excluding estimated forfeitures		$ 13,000	$ 13,000
2006 Equity Incentive Plan (2006 Plan) | Nonvested stock units issued (NSUs) | Award granted in 2012
Stockholders' equity
NSUs granted that will vest at the end of each of the three years after the performance goals are achieved (as a percent)			33.30%
Award vesting period of the grants			3 years
2006 Equity Incentive Plan (2006 Plan) | Nonvested stock units issued (NSUs) | Award granted in 2013
Stockholders' equity
NSUs granted that will vest at the end of each of the three years after the performance goals are achieved (as a percent)			33.30%
Award vesting period of the grants			3 years